Well known semiconductor components have a very high degree of integration and require many production steps performed in the wafer level compound leading to an expensive thermal load for the semiconductor component. Therefore the aim is to reduce the thermal load of the semiconductor component such that the maximal given thermal budget will not be exceeded.
Another viewpoint can be seen in the fact that assembling of semiconductor elements on substrates or printed circuit boards like the known BOC (board on chip) technology leads to the difficulty that different thermal expansion coefficients of the used components after assembling and during the burn-in or the later use leads to thermal tension between the components and the printed circuit board. This thermal tension results in an enormous mechanical load of the solder contacts. It is possible to reduce the thermal tensions by selection of suitable materials, but it is not possible to throw away the thermal tensions completely.
A significant improvement was reached by the development of the so-called elastec technology, which uses elastic or compliant contact elements made of an elastomer like silicon, so-called silicon bumps.
From the international laid open application published under the number WO 01/75969 A1, which is incorporated herein by reference, is known an electronic component with compliant contact bumps. The compliant contact bumps comprise rubber or silicon and can be self conductive or can be provided with a contact pad on the tip of it connected with a contact pad on the semiconductor element via a reroute layer.
Such reroute layers are made of metal with a multi layer structure with a nickel layer as the base covered by a copper layer and a gold layer coating the copper layer and protecting the copper layer from oxidation. The gold layer also secures a good solder ability of the contact pad on the tip of the compliant element.
The mentioned reroute layers are structured by the known technologies of photolithography to produce masks on the surface on the semiconductor component followed by metal deposition to realize the reroute layer itself and the contact pads simultaneously. It seems to be clear that it is not possible to avoid additional thermal load during the mentioned processes. Beyond, it is necessary to dismiss such semiconductor elements with faults in the structure of the reroute layer. This leads to financial disadvantages for the producer.
Assembling the compliant elements on the surface of the semiconductor component can be performed with the known technologies of printing especially by silk-screen printing.
Then the semiconductor components provided with the described contact elements are soldered on a substrate like a printed circuit board by such a way that every contact element on the semiconductor element is connected with a corresponding contact pad on the substrate usually by reflow soldering.